Olefin oxidation catalyst

ABSTRACT

The vapor phase oxidation of isobutene to methacrolein or methacrylonitrile (when NH3 is used as a reactant) is improved when an oxide of Na, K, Rb, Cs or Ca is added as a promoter to a catalyst containing the oxides of iron, molybdenum, tellurium and at least one of the oxides of rhenium, manganese and vanadium.

United States Patent Lane, Jr. Jan. 29, 1974 OLEFIN OXIDATION CATALYST 3,649,562 3/1972 Lane 252/439 3,658,927 4/1972 Crain et a1 [75] Invent $2 Lane' Lake Jacks, 3,716,496 2/1973 Yoshino et a1 252/439 [73] Assignee: h Dow Chemical Cmnpany, Primary Examiner-Patrick P. Garvin Mldland Mlch' Attorney, Agent, or Firm-William M. Yates et al. [22] Filed: May 8, 1972 [21] Appl. No.: 251,189 [57] ABSTRACT The vapor phase oxidation of isobutene to methacro- 252/439 260/604 lein or methac 'ylonitrile (when NH is used as a reac- [58] Fie'ld 439 tant) is improved when an oxide of Na, K, Rb, Cs or Ca is added as a promoter to a catalyst containing the 56] References Cited oxides of iron, molybdenum, tellurium and at least one of the oxides of rhenium, manganese and vanadium.

8 Claims, No Drawings 1 OLEFIN OXIDATION CATALYST BACKGROUND OF THE INVENTION The reaction of an olefin with O in the presence of a catalyst for producing unsaturated aldehydes is well known. Also well known is the reaction of olefins with O and NH to produce the corresponding unsaturated nitrile. These reactions have been classically carried out in the presence of various catalyst systems, including Cu O, Group lV(b) metals plus V and Mn, platinum group metals with Group V(a) promoters, phosphorous-containing catalysts, and, most recently, Te promoted catalyst systems.

U.S. Pat. No. 3,331,871 teaches a catalyst, M Ni, TeO Re for the oxidation of olefins. However, it is reported therein that butenes are converted primarily to carbon oxides, with only small amounts of unsaturated aldehydes or acids having four carbon atoms.

U.S. Pat. No. 3,401,197 reports a catalyst, Mo Te Group VIll metal P O for the oxidation of olefins.

Other molybdenum oxide-containing catalysts are known for preparing unsaturated aldehydes and acids from unsaturated hydrocarbons. One of these (U.S. Pat. No. 3,401,198) employs molybdenum oxide, tellruium oxide and an alkaline earth metal phosphate. U.S. Pat. No. 3,387,038 employs molybdenum oxide, an oxide of a group IIA metal, eg. magnesium or calcium and a promoter, among which are included iron, bismuth, antimony, tin and tellurium. U.S. Pat. No. 3,326,819 employs as a promoter a calcium or barium compound with a mixture of the oxides of antimony and tin. Other compounds of metals such as titanium, vanadium, iron, manganese and nickel may be used in place of, or together with, the calcium or barium compounds.

A US patent recently issued to the present inventor (No. 3,649,562) teaches the preparation of aldehydes and nitriles (when employing NH as a reactant) over a catalyst consisting essentially of oxides of iron, molybdenum, tellurium and at least one of the oxides of rhenium, manganese or vanadium.

Additional teachings of catalysts useful for making aldehydes from olefins may be found in U.S. Pat. Nos. 3,451,945 and 3,322,687.

SUMMARY OF THE INVENTION It has now been discovered that when the catalyst (described in U.S. Pat. No. 3,649,562) consisting essentially of the oxides of iron, molybdenum, tellurium and at least one of the oxides of rhenium, manganese and vanadium is promoted with one of the oxides of sodium, potassium, rubidium, cesium and calcium or mixtures thereof that the yield of methacrolein or methacrylonitrile is unexpectedly and substantially improved when the vapor phase oxidation of isobutylene is conducted in the presence of such catalyst. The oxide promoters are employed in amounts such that the atomic ratio of the metal to the other metals in the catalyst is from about 20 to 300 and preferably from about 50 to 200. Thus, an improved catalyst composition suitable for the oxidation of isobutylene to methacrolein and methacrylonitrile consists essentially of the oxides of Fe, Mo, Te and at least one of Re, Mn and V together with at least one promoter selected from the group consisting of oxides of Na, K, Rb, Cs, Ca and mixtures thereof, wherein the proportions of such oxides provides an atomic 'ratio of metals in accordance with the formula:

Fe Mo Te M Q, where x is 50 to 700, y is 500 to 1,300, 2 is 20 to and n is 20 to 300 and wherein M is Re, Mn, V or mixtures thereof and Q is Na, K, Rb, Cs or Ca.

Potassium has been found to be an especially good promoter in the process of the invention as illustrated by the following compositions:

FemMO oo0Te75Re K191 Fe Mo Te Re K Fe Mo Te Re K 100 isoo so 1 In like manner metal oxide catalysts having the following metal ratios were prepared in which sodium, cesium and calcium replaced the potassium:

FemMO1o00Te15Re Na 25 Fe Mo Te Re Ca The utilization of these catalysts is shown in Table l.

The oxidation and ammoxidation reactons of olefins and their equivalents are well known in the art. Operating conditions for the new catalysts are essentially the same as for known metal oxide catalysts. Suitably, the reactants should be contacted at a temperature of from about 200 to 500C., preferably at 300 to 400C and at 1-2 atmospheres or at pressure conditions which will keep the desired products in the vapor phase. An inert diluent may be utilized, such as nitrogen, steam, CO and saturated hydrocarbons.

A mole ratio of O lolefin of 0.1/1 to 15/1 is suitable while 0.5/1 to 6/1 is preferred. A mole ratio of diluent/O of 0/1 to 50/1 is also suitable, while 15-65 volume percent of total feedis preferred. 1n the ammoxidation reaction, a mole ratio of NH /isobutylenc of from 0.5 to 10 is acceptable, while as little as possible to effect complete conversion of aldehyde to nitrile is preferred.

Oxygen and oxygen-containing gases, such as air, are suitable for the oxidizing agent. Ammonia and lower primary alkyl amines and alkylene diamines, such as methylamine, n-butylamine and ethylenediamine, are suitable for the ammoxidation reaction. The product obtained using primary amines, in place of Nl-l however, is a Schiff base rather than a nitrile.

Products which can be prepared from isobutylene include methacrolein and methacrylonitrile.

The catalysts of this invention are prepared by combining the metal salts or oxides in water'in a flask with stirring. If neutralization is desired (may be necessary when metal supports are used) ammonia solution is added until the neutral point is reached. The product is transferred to a tray where stirring and warming in air dehydrates the slurry. A support may be added during the dehydration. The product is then broken up for use, or powdered and pelleted. Molybdenum is usually added as ammonium-p-molybdate, but M00, or other Mo compounds are acceptable. Similarly, ammoniumm-vanadate, V 0 and similar compounds may be used as the vanadium component. Iron and manganese may be added as nitrates, oxides or other salts; tellurium is usually added in the form of the oxide, TeO Tellurium metal or a metal tellurate may be dissolved in an acid,

e.g. l-lCl, before use. Rhenium may be added as perrhenic acid or as a salt of the metal.

The promoter metal oxides may be added as soluble salts of the metals. Thus, sodium, potassium, cesium,

The above catalyst contained the oxides of Fe, Mo, Te, Re and K in proportions such that the ratios of the metal atoms was 600:1,000275zlz191, respectively. Other catalysts were made in similar manner wherein calcium hydroxide, cesium nitrate and sodium carbonate were used in place of the potassium carbonate. Salts such as rubidium chloride, cesium nitrate, potassium nitrate and sodium chloride also can be used.

Example 2 Oxidation Reactions The reactors were 22 inch or inch stainless steel tubes (78 inches long), arranged vertically, with Nirubidium and calcium may be added to the solution for 5 chrome wire spiral catalyst supports at the bottom. The the preparation of the solution for the preparation of flow was downward. the catalyst as carbonates, chlorides, nitrates, and the The reactor tubes were housed in a shell (6 inch l.D. like which are soluble in water or aqueous acid soluby 4 feet long) which contained 2 gallons of polyphenyl tions. ether (bathing 48 inches of the reactor). The bath was Supports may be carborundum, firebrick, silica, alu- 10 heated by 4 immersion heaters and 4 wall heaters. The mi l d i il commercial supports known unit was well insulated. Thermocouples were placed to the art. The preferred supports are metal particles of every 6 inches vertically and a thermoswltch (2 feet good heat capacity and heat transfer properties such as from the reactors bottom) was Present to Prevent aluminum granules, copper, silver or lead shot or iron away heating in case of vacuum pump failure. Full vacparticles. Surface area of the catalyst is preferably 5 to Hum produced about 4 mm. Hg pressure n he eaC Or 50 sq. meters/gram. shell. Specific Embodiments The reactors temperatures varied between about Example 1 Catalyst Preparation 330 and 370C (depending upon the vacuum setting) Distilled water (300-400ml.) was placed in a 2-liter, where contacting the liquid and about to 365C 4-necked round-bottomed, borosilicate fl k i d "where contacting the vapor. The reported reaction with a condenser, stirrer, thermometer, pressuretemperature was the measured temperature of the boilequalizing addition funnel and heating mantle. Ammong fl id, Since the catalyst volume was adjusted to give nium heptamolydate'4H O (88.3 g.) was added to the a level below the top of the heat transfer liquid in the water and the stirring mixture was warmed to 50C. reactors shell. The vapor area above the catalyst zone Ferric nitrate-9H O 121.1 g.) was dissolved in 250 ml. acted as a preheater zone. H 0 and the solution was added dropwise to the flask. Results are given in Tables I and II below. Contact timewas calculated from the formula; Perrhenic acid (0.125 g.) was dissolved in 10 ml. of water and was poured into the flask. Tellurium dioxide 1 (5.93 g.) was added slowly to stirred concentrated HCl Bulk cat. VOL

solution (35.50 ml.); when dissolved, the solutlon was Contact Ilme, 860-:

. Gas feed flow, cc/mm. Mln. added cautlously dropwise to the flask. Stlrrlng was It a co tmued nd potassium (6 6 g added Room Temp. K Pressure at reactor lnlet, psla. 1 The product was poured lnto a glass tray which was o heated on a steam cone under an infrared lamp with 35 Reactor fluld K Atmosphenc pressure p513 constant stirring until the product solidified. The product was calcined at 300C for 2 hours. The solid remaining was a light green, yellow, or brown lumpy ma- When reactor inlet pressure was less than 2 psig, no terial, weighing about grams. It was broken into pressure correction was used in the above formula. All pieces, powdered and pelleted to give good pellets of 40 of the following runs were at pressures below 2 psig, so QW fin s QQDWHL no pressure correction was required.

TABLE 1 OXIDATION OF ISOBUTENE USING SELECTED PROMOTERS Gas Vol. To Yield Run TC Contact Feed C,H,, Air N2 Promoter Olefin CO, CO Methacrolein Time Sec. Atomic Conv.

Ratio l 335 2 2.1 58.9 Bal. 1611107 99.9 24.6 13.7 55.8 2 350 3 1.5 58.9 Bal. K( 191 99.9 14.8 5.2 81.5 3 335 3 1.8 58.9 Bal. 1( 191 98.0 13.3 4.7 74.5 4 335 2 2.2 58.9 Bal. Na() 99.8 12.2 3.5 73.9 5 335 6 2.2 58.9 Bal. 88(65) 99.9 41.5 15.5 34.7 6 340 6 1.7 58.9 Bal. None 96.0 27.9 14.6 57.5 7 335 15 1.8 58.9 Bal. (35 77 78.7 9.9 2.7 78.0 8 335 5 1.9 58.9 Bal. None 77.0 27.9 8.9 47.5 9 335 6 1.5 58.9 Bal. Ca(172) 49.0 6.2 4.7 70.2 10 335 4 1.6 58.9 Bal. None 51.6 51.6 8.46 50.7

In the above Table l, Runs 1 and 5 are not examples of the invention, but are shown to illustrate the unexpected properties of the promoters selected from Group IA and Group "A. Thus, Li and Ba do not have the property of promoting the catalyst. Runs 6, 8 and 10 are illustrative of the catalyst without the promoters l and are presented to show a comparison with the pro- Mo, Te and at least one of Re, Mn and V together with at least one promoter selected from the group consisting of oxides of Na, K, Rb, Cs, Ca and mixtures thereof, wherein the proportions of such oxides provides an atomic ratio of metals in accordance with the formula:

Fe Mo Te M 0,.

TABLE I1 OXIDATION OF ISOBUTENE Feed Gas, Vol. 7c

Run TC Contact C,H Air N NH Promoter Conv. 7c CO, CO Methacrylonitrile Time Sec. Atomic Methacrolein Ratio 11 340 6 2.0 58.9 Bal. K( 191) 58.9 7.8 4.5 76.4

13 335 6 1.62 58.0 Bul. K( 191) 87.0 13.0 4.1 78.8

14 330 6 1.82 58.9 36.0 33 K(l9l) 91.0 16.4 2.5 53.7 8.6

Strum replaced nitrogen in this run Note particularly that Run 1 1 uses a somewhat higher proportion of isobutylene in the feed and that Runs 12 and 13 compare favorably even though steam is used in the former in place of the nitrogen as a diluent. Run 14 shows that methacrylonitrile is produced when ammonia is introduced into the feed gas. A higher than usual temperature is employed in Run 15 with yield of methacrolein remaining high.

Propylene was also fed to the catalyst disclosed in the inventors earlier patent and then the same catalyst containing the promoters of the instant invention was used to oxidize propylene. There was no substantial difference in the yield of acrolein obtained with and without the promoter, thus giving further evidence of the unexpected nature of the instant disclosure with respect to the oxidation of isobutylene.

I claim:

1. An improved catalyst composition suitable for the oxidation of isobutylene to methacrolein and methacrylonitrile consisting essentially of the oxides of Fe,

where x is 50 to 700, y is 500 to 1,300, 2 is 20 to 80 and n is 20 to 300 and wherein M is Re, Mn, V or mixtures thereof, and Q is Na, K, Rb, Cs or Ca.

2. The catalyst composition of claim 1 in which M is rhenium and Q is potassium.

3. The catalyst composition of claim 1 in which M is rhenium and Q is sodium.

4. The catalyst composition of claim 1 in which M is rhenium and Q is cesium.

5. The catalyst composition of claim 1 in which M is rhenium and Q is calcium.

6. The catalyst composition of claim 1 wherein the atomic ratio of the metals is Fe Mo, Te, Re, Q,,, where n is 50 to 200.

7. The catalyst composition of claim 6 wherein Q is potassium.

8. The catalyst composition of claim 1 wherein M is rhenium, Q is potassium, x is 600, y is 1,000, z is and n is 191. 

2. The catalyst composition of claim 1 in which M is rhenium and Q is potassium.
 3. The catalyst composition of claim 1 in which M is rhenium and Q is sodium.
 4. The catalyst composition of claim 1 in which M is rhenium and Q is cesium.
 5. The catalyst composition of claim 1 in which M is rhenium and Q is calcium.
 6. The catalyst composition of claim 1 wherein the atomic ratio of the metals is Fe600Mo1000Te75Re, Qn, where n is 50 to
 200. 7. The catalyst composition of claim 6 wherein Q is potassium.
 8. The catalyst composition of claim 1 wherein M is rhenium, Q is potassium, x is 600, y is 1,000, z is 75 and n is
 191. 